/*
 * Compilation Copyright (c) 1995-2019 by Wei Dai.  All rights reserved.
 *	This copyright applies only to this software distribution package
 *	as a compilation, and does not imply a copyright on any particular
 *	file in the package.
 * 
 *	Boost Software License - Version 1.0 - August 17th, 2003
 *
 *	Permission is hereby granted, free of charge, to any person or organization
 *	obtaining a copy of the software and accompanying documentation covered by
 *	this license (the "Software") to use, reproduce, display, distribute,
 *	execute, and transmit the Software, and to prepare derivative works of the
 *	Software, and to permit third-parties to whom the Software is furnished to
 *	do so, all subject to the following:
 * 
 *	The copyright notices in the Software and this entire statement, including
 *	the above license grant, this restriction and the following disclaimer,
 *	must be included in all copies of the Software, in whole or in part, and
 *	all derivative works of the Software, unless such copies or derivative
 *	works are solely in the form of machine-executable object code generated by
 *	a source language processor.
 *
 *	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 *	IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 *	FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
 *	SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
 *	FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
 *	ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 *	DEALINGS IN THE SOFTWARE.
 */

// emsa2.h - originally written and placed in the public domain by Wei Dai

/// \file emsa2.h
/// \brief Classes and functions for various padding schemes used in public key algorithms

#ifndef CRYPTOPP_EMSA2_H
#define CRYPTOPP_EMSA2_H

#include "cryptlib.h"
#include "pubkey.h"
#include "hashfwd.h"
#include "misc.h"

#ifdef CRYPTOPP_IS_DLL
# include "sha.h"
#endif

NAMESPACE_BEGIN(CryptoPP)

/// \brief EMSA2 hash identifier
/// \tparam H HashTransformation derived class
/// \since Crypto++ 5.0
template <class H> class EMSA2HashId
{
public:
	static const byte id;
};

/// \brief EMSA2 padding method
/// \tparam BASE Message encoding method
/// \since Crypto++ 5.0
template <class BASE>
class EMSA2HashIdLookup : public BASE
{
public:
	struct HashIdentifierLookup
	{
		template <class H> struct HashIdentifierLookup2
		{
			static HashIdentifier Lookup()
			{
				return HashIdentifier(&EMSA2HashId<H>::id, 1);
			}
		};
	};
};

// EMSA2HashId can be instantiated with the following classes.
// SHA1, SHA224, SHA256, SHA384, SHA512, RIPEMD128, RIPEMD160, Whirlpool

#ifdef CRYPTOPP_IS_DLL
CRYPTOPP_DLL_TEMPLATE_CLASS EMSA2HashId<SHA1>;
CRYPTOPP_DLL_TEMPLATE_CLASS EMSA2HashId<SHA224>;
CRYPTOPP_DLL_TEMPLATE_CLASS EMSA2HashId<SHA256>;
CRYPTOPP_DLL_TEMPLATE_CLASS EMSA2HashId<SHA384>;
CRYPTOPP_DLL_TEMPLATE_CLASS EMSA2HashId<SHA512>;
#endif

// https://github.com/weidai11/cryptopp/issues/300 and
// https://github.com/weidai11/cryptopp/issues/533
#if defined(__clang__)
template<> const byte EMSA2HashId<SHA1>::id;
template<> const byte EMSA2HashId<SHA224>::id;
template<> const byte EMSA2HashId<SHA256>::id;
template<> const byte EMSA2HashId<SHA384>::id;
template<> const byte EMSA2HashId<SHA512>::id;
#endif

/// \brief EMSA2 padding method
/// \since Crypto++ 5.0
class CRYPTOPP_DLL EMSA2Pad : public EMSA2HashIdLookup<PK_DeterministicSignatureMessageEncodingMethod>
{
public:
	CRYPTOPP_STATIC_CONSTEXPR const char* CRYPTOPP_API StaticAlgorithmName() {return "EMSA2";}

	size_t MinRepresentativeBitLength(size_t hashIdentifierLength, size_t digestLength) const
		{CRYPTOPP_UNUSED(hashIdentifierLength); return 8*digestLength + 31;}

	void ComputeMessageRepresentative(RandomNumberGenerator &rng,
		const byte *recoverableMessage, size_t recoverableMessageLength,
		HashTransformation &hash, HashIdentifier hashIdentifier, bool messageEmpty,
		byte *representative, size_t representativeBitLength) const;
};

// EMSA2, for use with RWSS and RSA_ISO
// Only the following hash functions are supported by this signature standard:
//  \dontinclude emsa2.h
//  \skip EMSA2HashId can be instantiated
//  \until end of list

/// \brief EMSA2/P1363 padding method
/// \details Use with RWSS and RSA_ISO
/// \since Crypto++ 5.0
struct P1363_EMSA2 : public SignatureStandard
{
	typedef EMSA2Pad SignatureMessageEncodingMethod;
};

NAMESPACE_END

#endif
